Fig. 4.

Schematic figure displaying the mechanism of the synergistic effect of IFN-γ and IL-1β on PD-L1 expression. A potential mechanism of the synergistic effect of IFN-γ and IL-1β on PD-L1 expression is that (1) IFN-γ and IL-1β synergistically increase the expression of transcription factor IRF-1, which regulates PD-L1 expression; and (2) IL-1β enhances IFNGR expression, which consequently enhances IFN-γ signal transduction and leads to an increase in PD-L1 expression. STAT1, NF-κB, and p38 MAPK may be involved in these mechanisms.